1. Field of the Invention
The present invention pertains to a package for circuit boards and other electronic assemblies having a continuous conductive surface thereon to protect the package contents against electrostatic discharge. The package is manufactured from plastic sheet on which a conductive substance is deposited over substantially the entire outer and/or inner surface of the package.
2. Background
The development of microelectronic circuits and devices utilized in such circuits, including metal oxide semiconductors, transistors and other devices, has created a serious problem in the handling, shipping and storage of various circuit devices, including printed circuit boards, due to the generation of static electricity. The buildup of electrostatic charges on various elements such as packaging and virtually any object which comes into contact with microelectronic circuits can cause critical damage to the circuits which can remain undetected until the circuit is placed in use or can shorten the useful life of such circuits. The electrostatic charges can, of course, originate in various ways but the ordinary handling of electronic circuit boards and other devices through movement of the device by mechanical means or by the person manufacturing or installing the device can result in serious electrical damage to circuit components.
To this end there have been efforts to develop packaging and handling devices which are provided with a conductive surface to constantly drain away or prevent the buildup of an electrostatic charge on the package or to prevent the transfer of a charge on an object which comes into contact with the package to the circuit element contained in the package.
The large scale manufacture of various types of microelectronic circuit boards and other devices has accentuated the need for low cost reliable packaging in which circuit boards and other elements can be shipped, stored and otherwise handled without risk of damaging the circuit from electrostatic discharges. The package should, of course, provide the function of supporting and protecting the circuit from physical damage due to impact of the package with other objects during its handling and shipping. The package should also be capable of large scale, low cost manufacture and, in particular, it has been determined that the package must be capable of being provided with a continuous electrically conductive surface which will adequately shield the contents of the package from electrostatic discharges.
Although various packages have been developed for storing and shipping electronic printed circuit boards and other microelectronic devices, one of the major problems with prior art packages is the failure to provide a container which is structurally simple and low cost of manufacture, which is adapted to support the electronic device packed therein to permit relatively little or no movement of the device within the package, be capable of absorbing relatively high impact loads from dropping the package or from striking the package with other objects and be reliable as regards the conductivity of static charges to prevent a charge buildup on a portion of the package which may eventually come into direct contact with the circuit board or through another conductive element such as the person handling the circuit board on removal from the package. The provision of paperboard packages which have been coated on an inside or outside surface are not entirely satisfactory since the packages must be glued or mechanically fastened together to form a suitable enclosure thus introducing the possibility of forming a discontinuity in the conductive surface of the package. Known types of packages, including paper or particle board packages or packages requiring conductive insert type structures for supporting the packaged device, are also not capable of high volume, low cost manufacture. Those types of packages requiring conductive material insert members also require additional space to accommodate the insert structure which adds to package shipping and storage costs. Accordingly, there has been an unfilled need for an electrically conductive package for storing and shipping electronic circuit elements and similar devices and which has all of the features and advantages described herein.